fixed YARD documentation for mrb_obj_new

Updated mruby.h YARD doc.

Merge branch 'fix_androidndk_rake' of https://github.com/crimsonwoods/mruby into crimsonwoods-fix_androidndk_rake

Rename androidndk tolchain to just android

use androidndk.rake which is better and 64bit aware

mrb_get_mid and mrb_get_argc

Wrote YARD docs for mrb_define_module, mrb_include_module, mrb_prepen…

Update androidndk.rake to add support 64bit architectures.

Wrote YARD docs for mrb_define_module, mrb_include_module, mrb_prepend_module, mrb_define_class_method, mrb_define_module_function, and mrb_define_const on mruby.h

'mips64' can integrate into 'mips'.
'x86_64' is the same as 'mips64'.

This is the first step of implementing 'ldflags'.